Mean (top) and anomalous (bottom) 200-hPa streamfunction (CDAS/Reanalysis).
Contour interval is
20 x 106 m2s-1
(top) and 5 x 106 m2s-1
(bottom). Negative (positive) values are indicated by dashed (solid) lines.
The non-divergent component of the flow is directed along the contours with
speed proportional to the gradient. Thus, high (low) stream function
corresponds to high (low) geopotential height in the Northern Hemisphere
and to low (high) geopotential height in the Southern Hemisphere.
Anomalies are departures from the 1981-2010 base period monthly means.